In order to study the effect of water film on aerodynamic charactristics of the fan

the mean square thickness of water film on blade surface was calculated by using water film equation combined with the parameters of the water droplets colliding with the wall surface. Then the sand grain roughness model was added to the numerical calculation to simulate the change of blade surface roughness caused by water film. Fan blades were numerically simulated under different rain ingestion rates and water droplet diameters. Results indicate that water film mainly distributes in the leading edge and root region of blade pressure surface. The water film’s thickness and depositional area are positively correlated with rain ingestion rate. In addition

the existence of water film can reduce the pressure ratio and temperature ratio of the fan. When the average diameter of the water droplet is 1000μm and the rain ingestion rate is 5%

thewater droplet depositionalarea is 0.0758m2

accounting for 33.91% of the pressure surface area of the blade.